| 摘要 |
PURPOSE:To enhance heat resistance while dispensing with a light guide, by covering one end of a columnar space with the part of the glass window of a scintillator and covering the other end thereof with the light incident part of a photomultiplier. CONSTITUTION:When radioactive rays from above transmit through a lid 23 and a container 2 to be incident to a scintillator 1, the fluorescent substance in the scintillator emits light which in turn transmits through a glass window 3, a space 22 and a glass plate 7 to enter a photomultiplier from a light receiving part 6 and, herein, said light is converted to an electric signal to perform the detection of radioactive rays. That is, because the optical coupling of the scintillator 1 and the photomultiplier 5 is performed in the space 22 without using a light guide, the detector does not become heavy. Because films 4 are respectively provided to the glass window 3 and the glass plate 7, light is reduced in reflection and attenuation when transmits through both of them and the lowering in detection efficiency is prevented. When air is injected into a first detection tube 29a, it is exhausted from an exhaust port 32 through connection tube 29a first conduit 28a space 22 second conduit 28b second connection tube 29b to perform ventilation and heat resistance is enhanced because the temp. of the photomultiplier 5 is not raised.
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